Culm height and susceptibility of Canadian winter and spring wheat cultivars to common bunt (Tilletia tritici and T. laevis)

Abstract

A field study involving winter and spring wheat cultivars possessing race-specific and nonspecific resistance to Tilletia tritici and T. laevis was conducted to determine the effect of bunt on culm dwarfing, and the role of culm height in the susceptibility of wheat cultivars. Bunt-induced stunting, ranging from 2.4 to 21%, was observed in 20 of 25 cultivars and the severity was correlated with level of bunt (r = 0.86). Also, there was preferential infection of shorter culms by the bunt fungus and this appeared to be a major factor in the susceptibility of most cultivars in this study. Cultivars possessing moderate to high levels of nonspecific resistance such as Katepwa and Chinook had fewer short culms; these short culms were susceptible. A large proportion of the culms of short-statured or semi-dwarf cultivars such as HY320, Tobari 66, and the soft white spring wheats Fielder and Springfield, fell into the shortest height classes; uniformly these were highly susceptible to bunt infection. Laura and Roblin, cultivars of conventional height, had a large proportion of short culms and these were highly susceptible. Red Bobs 222 and HY355 also exhibited high levels of bunt in the taller culms. Cultivars possessing race-specific resistance such as the durum wheats and BW553 had low levels of infection across the culm height classes. Cultivar variation in susceptibility to bunt within each of the different culm height classes also was observed. The possible implications of the effect of preferential bunting of short culms on development in short-statured or semi-dwarf wheats are discussed. Key words: Stinking smut, Norin 10/Brevor